1. Field of the Invention
This invention relates broadly to surgical instruments. More particularly, this invention relates to a surgical snare instrument for excising polyps.
2. State of the Art
Surgical snare instruments are used for the endoscopic removal of hypertrophic tissue growths within a body cavity, and particularly within the colon. Snare instruments generally include an elongated tubular member, such as a catheter sheath, a shaft extending through the tubular member, and an elastic wire (e.g., stainless steel or Nitinol) forming a loop movable distally and proximally within the tubular member. The loop can be opened by moving the loop beyond the distal end of the tubular member and closed by retraction into the tubular member, each effected by movement of the shaft relative to the sheath. A handle is provided at the proximal end of the instrument to facilitate this movement.
With the loop of the snare instrument in a retracted position, the distal end of the instrument is inserted through an endoscope into the colon and moved adjacent a polyp or other tissue growth which is identified for removal. The handle of the instrument is then operated to expand the loop of the snare and an attempt is made to maneuver the loop to surround the polyp. If successful, the loop is then constricted about the polyp to excise it. Additionally, the snare instrument may be provided with cautery capability in order to limit bleeding and thereby enhance the polyp removal procedure.
It will be appreciated that manipulation of the loop of the snare instrument about the polyp is a difficult, and sometimes unattainable, task. The expanded snare loop often lies in a plane which is not conducive for maneuvering about the polyp. Therefore, the desired polyp retrieval often cannot be achieved with the snare instrument and a more invasive procedure may be required to remove the hypertrophic growth. None of the prior art provides a means for rotating the snare loop into another plane of orientation to facilitate growth entrapment. Furthermore, none of the prior art even addresses this need.
It is however known in the laparoscopic art to provide means for permitting end effectors of laparoscopic instruments to be rotated relative to the tubular sheath of the instrument. However, laparoscopic instruments typically are relatively short devices and utilize a relatively stiff control rod which effectively translates rotational movement from the proximal end to the distal end of the instrument. As such, laparoscopic instruments are not subject to the difficulties presented by the need to rotate flexible shafts.
In addition, U.S. Pat. No. 5,788,710 to Bates et al. discloses an endoscopic mechanical lithotripsy instrument for crushing calculi in the gastrointestinal tract. The instrument includes a distal basket assembly and purports to permit controlled rotation of the basket assembly via proximal manipulation. The instrument includes a relatively long tubular sheath (typically up to eight feet in mechanical lithotripsy instruments), a 4xc3x977 stainless steel flexible cable shaft of similar length extending through the sheath, a handle at the proximal end of the device for moving the shaft relative to the sheath and for applying torsional force to the proximal end of the shaft, and the surgical basket assembly at the distal end of the sheath for entrapping and crushing a calculus. While Bates et al. states that rotating the proximal end of the shaft, via the handle, causes a like amount of rotation of the basket assembly about the longitudinal axis of the instrument, it has been found that the described cable shaft does not function as described to provide the controlled rotation. The stainless steel cable shaft is incapable of translating the proximal torque into controllable movement of the distal basket. Rather, when rotational movement is applied to the proximal end of the shaft, the proximal end of the shaft twists without imparting any movement to the distal end of the instrument until sufficient torsional force is stored in the shaft to cause the basket assembly to rotate rapidly and uncontrollably to release the stored force.
It is therefore an object of the invention to provide a surgical instrument having a relatively long flexible shaft, wherein rotation of the proximal end of the shaft is translated into controlled rotation of the distal end of the shaft.
It is another object of the invention to provide a surgical snare instrument having a relatively long flexible shaft, wherein rotation of the proximal end of the shaft is translated into controlled rotation of the distal end of the shaft thereby permitting a snare loop at the end of the shaft to be rotatably oriented.
It is a further object of the invention to provide a surgical snare instrument which includes a proximal handle which permits rotation of a proximal end of the shaft, and a shaft adapted to provide rotation of the distal end of the instrument in a one to one ratio with rotation of the proximal end.
It is an additional object of the invention to provide a surgical snare instrument having a handle which is adapted to rotate the proximal end of the shaft and a shaft which translates the proximal rotation into controlled rotation of the distal end of the shaft, and which further includes cautery capability.
In accord with these objects, which will be discussed in detail below, a surgical snare instrument is provided. The snare instrument includes an elongated tubular sheath having proximal and distal ends, a flexible torqueable shaft having proximal and distal ends extending through and axially movable relative to the sheath, a snare loop at the distal end of the shaft, and a handle assembly coupled to the proximal ends of the sheath and shaft for moving the shaft axially and rotatably relative to the sheath so that the snare loop, when axially moved beyond the distal end of the sheath, is rotatable relative to the distal end of the sheath.
The flexible shaft is preferably a multifilament twisted and drawn cable. The filaments of the multifilament twisted and drawn cable are preferably either stainless steel, nickel-titanium alloy, or a combination of the two. Such a shaft provides the high torqueability necessary for controlled rotation of the snare loop. In addition, the shaft is capable of carrying a cautery current.
In a first preferred embodiment of the handle, the handle assembly includes a stationary member and a movable member axially and rotatably movable relative to the stationary member. The stationary member has a proximal thumb ring, a distal coupling to which the sheath is coupled, and a central longitudinal slot in communication with the sheath. The movable member includes two finger rings (fixed relative to each other) for facilitating relative axial and rotational movement of the movable member. A relatively rigid drive shaft provided with a pinion is coupled to the proximal end of the flexible shaft and extends through the longitudinal slot of the stationary member. A mounting member includes a bore in which the proximal end of the drive shaft is received and in which the drive shaft is permitted to rotate. The movable member is coupled to the mounting member so that the movable member may be pivoted about a line transverse to the drive shaft. The movable member is provided with a plurality of teeth arranged along a radial arc forming a rack which engages the pinion of the drive shaft. As such, axial movement of the movable member relative to the stationary member causes the loop at the distal end of the flexible shaft to be moved axially in and out of the tubular sheath. In addition, pivoting the movable member relative to the mounting member causes the rack to rotate the pinion and, consequently, the drive shaft and flexible shaft coupled thereto. Furthermore, the stationary member may be provided with a cautery assembly permitting a cautery current to be applied to the flexible shaft and the snare loop.
According to a second embodiment of the invention, the handle assembly includes a stationary member and a slidable member axially movable relative to the stationary member. The flexible shaft is coupled to the slidable member in a manner which does not permit rotation of the slidable member relative to the flexible shaft. The proximal end of the sheath is coupled to the stationary member so as to permit the stationary member and the flexible shaft to be rotated relative to the sheath. A stabilizing member may be fixedly coupled over a proximal portion of the sheath to facilitate relative rotational movement of the flexible shaft and sheath. As such, the slidable member may be moved relative to the stationary member to deploy and retract the snare loop, and the entire handle may be rotated relative to the sheath, facilitated by use of the stabilizing member, to rotate the snare loop relative to the distal end of the sheath. In addition, the handle may be adapted to provide cautery capability to the snare loop.
According to a third embodiment of the invention, the handle assembly includes a first member having a thumb loop and a longitudinal slot, and a second member slidably positioned within the slot and coupled to the proximal end of the flexible shaft. A third member having a longitudinal bore and a cautery plug assembly is provided relatively distal the first member. The third member is rotatably coupled to the first member so that the slot and bore are axially aligned. In addition, the proximal end of the sheath is coupled to the distal end of the third member in alignment with the bore. Axial movement of the second member relative to the first member causes axial movement of the flexible shaft relative to the sheath and resultant deployment and retraction of the snare loop. Rotational movement of the first and second members relative to the third member causes rotational movement of the snare loop relative to the sheath.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.